// 3. 抽象同事  员工
public abstract class Colleague
{
  protected IMediator Mediator;
  public string Name { get; }

  protected Colleague(IMediator mediator, string name)
  {
    Mediator = mediator;
    Name = name;
  }

  public void Send(string message)
  {
    Console.WriteLine($"{Name} 发送: {message}");
    Mediator.Send(message, this);
  }

  public virtual void Receive(string message, Colleague sender)
  {
    Console.WriteLine($"{Name} 收到 {sender.Name}: {message}");
  }
}